Vitamin D supplements may have no benefit to healthy adults
Without sufficient vitamin D, bones can become thin, brittle, or misshapen.
London (PRWEB UK) 16 October 2013
Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis. Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal mineralization of bone and to prevent hypocalcemic tetany. It is also needed for bone growth and bone remodelling by osteoblasts and osteoclasts. Without sufficient vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults. 1
Many studies have been undertaken to define the exact quantity of Vitamin D required for individuals of all ages. In the paper entitled "Vitamin D Deficiency Induces Early Signs of Aging in Human Bone, Increasing the Risk of Fracture" Robert Ritchie from the University of California (UC) Berkeley's Materials Science and Engineering Department and Björn Busse, of the Department of Osteology and Biomechanics at the University Medical Center in Hamburg, Germany stated that "The assumption has been that the main problem with vitamin D deficiency is reduced mineralization for the creation of new bone mass, but we've shown that low levels of vitamin D also induces premature aging of existing bone."
“We hypothesized that restoring the normal level of vitamin D not only corrects the imbalance of mineralized and non-mineralized bone quantities, but also initiates simultaneous multiscale alterations in bone structure that affects both the intrinsic and extrinsic fracture mechanisms," Ritchie says.
To test this hypothesis, Busse and his German team collected samples of iliac crest bone cores from 30 participants, half of whom were deficient in vitamin D and showed early signs of osteomalacia. The bone samples were sent to Ritchie and his team for analysis at the ALS using Fourier Transform Infrared (FTIR) spectroscopy and X-ray computed microtomography.
Says Ritchie, “In situ fracture mechanics measurements and CT-scanning of the crack paths indicated that vitamin D deficiency increases both the initiation and propagation of cracks by 22- to 31-percent." From their study, Busse, Ritchie and their co-authors say that vitamin-D levels should be checked and kept on well-balanced levels to maintain the structural integrity of bones and avoid mineralization defects and aging issues that can lead to a risk of fractures. 2
Recently, at the University of Auckland, researchers analysed 23 randomised trial studies examining the effects of vitamin D supplementation on bone mineral density in healthy adults from the UK, the US, Australia, Holland, Finland and Norway. This meta-analysis involved more than 4,000 healthy people who took Vitamin D supplements for two years up to July 2012. Prof Ian Reid, lead study author, from the University of Auckland, said the findings showed no significant difference in the bone density, except around the femoral neck, indicating that healthy adults did not need to take vitamin D supplements.
"Our data suggest that the targeting of low-dose vitamin D supplements only to individuals who are likely to be deficient and to prevent osteoporosis could free up substantial resources that could be better used elsewhere in healthcare. However, maintenance of vitamin D stores in the elderly combined with sufficient dietary calcium intake remains an effective approach for prevention of hip fractures." 3 Dr Laura Tripkovic, research fellow in the department of nutritional sciences at the University of Surrey, added that it was no good taking vitamin D supplements if people didn't also maintain a healthy, balanced diet containing calcium and take plenty of exercise.
The Department of Health currently recommends that a daily supplement of vitamin D of 10 micrograms (0.01mg) should be taken by pregnant and breastfeeding women and people over 65, while babies aged six months to five years should take vitamin drops containing 7 to 8.5 micrograms (0.007-0.0085mg) per day. The UK guidance is currently being reviewed. 4
1. http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
2. http://stm.sciencemag.org/content/5/193/193ra88
3. http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(13)61647-5/abstract
4. http://www.bbc.co.uk/news/health-24473156